The present invention relates to a seed drill with a frame, reservoirs, sowing shares at least two separate inlets and outlets for two different materials, and a depth-guide or pressure roller behind each sowing share, with variable amounts of one material being conveyed to the forward outlet and of the other material to the rear outlet through separate channels inside the sowing shares for application in the soil, with the outlets separated along the direction of travel, and with a narrow ripping structure on the forward edge of each sowing share to rip up the soil and produce a furrow.
A seed drill of this type is known from U.S. Pat. No. 4,417,530 and from German OS No. 3 216 375. The sowing share of this seed drill, which is intended for zero tillage, draws a V-shaped furrow in the uncultivated soil. The initial material, either seed or fertilizer, is deposited on the base of the furrow in the narrow cross-section at the point of the V. Once the material has been deposited, the expelled soil flows back into the furrow and covers the material. The second material is then deposited in a ribbon or in two rows in the soil that has flowed back into the furrow. Finally the soil in the furrow and hence the seed and fertilizer is packed down with a smooth pressure roller.
The drawback to this machine is that it is impossible to pack the material initially deposited in the furrow, tightly enough against the soil or to pack down the soil in the furrow firmly enough in the vicinity of the seed. Furthermore, it is impossible, especially if the soil is heavy, to ensure satisfactory separation of the two materials because the soil does not flow back into the furrow fast enough, so that either very little soil separates them or they are deposited together.
A special drawback of the seed drill described in U.S. Pat. No. 4,417,530 is that as a result of the design of the sowing share the soil is dug up very powerfully. Since the pipelines for depositing the second material in two separate rows do not return enough soil before the second material is deposited, and separate deposit of the seed and fertilizer cannot be guaranteed.
The disadvantage of a sowing share known from German Pat. No. 3 332 352 is that the conductor 47 is relatively complicated and can only be manufactured with complicated molds.